Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$58.25	3.333%	$60.1915	$60.19	$60.20	$60.20
Purchase #2	$80.31	7.552%	$86.375	$86.38	$86.40	$86.40
Purchase #3	$57.43	9.265%	$62.7509	$62.75	$62.75	$62.80
Purchase #4	$217.51	8.539%	$236.0832	$236.08	$236.10	$236.10
Purchase #5	$47.71	9.784%	$52.3779	$52.38	$52.40	$52.40
Purchase #6	$75.95	8.145%	$82.1361	$82.14	$82.15	$82.10
Purchase #7	$89.56	12.690%	$100.9252	$100.93	$100.95	$100.90
7 purchase totals =	$626.72		$680.8398	$680.85	$680.95	$680.90